Battery monitoring apparatus

ABSTRACT

A battery monitoring apparatus monitors a state of a nickel hydrogen battery. The apparatus includes a board having a high voltage part having a voltage detection section detecting a voltage of the nickel hydrogen battery, and a low voltage part operating at voltage lower than voltage of the high voltage part, a housing that accommodates the board, and an attachment member that is attached to an opposed portion of the housing, which is opposed to a board surface of the board to attach the housing to a predetermined position. A passage is formed between the opposed portion and the attachment member. The passage extends from an opening part provided at a circumference part of the housing and along the opposed portion. The passage is located at a position that overlaps with the low voltage part, when viewed in a normal direction of the board surface.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on and claims the benefit of priority fromearlier Japanese Patent Application No. 2014-256060 filed Dec. 18, 2014,the description of which is incorporated herein by reference.

BACKGROUND

1. Technical Field

The present invention relates to a battery monitoring apparatus, inparticular, a battery monitoring apparatus that monitors a state of anickel hydrogen battery.

2. Related Art

As a secondary battery for a vehicle in which the driving force isgenerated by an electric motor, a nickel hydrogen battery is known. Thenickel hydrogen battery has a negative electrode made of a hydrogenstoring alloy and a positive electrode made of a nickel compound such asnickel hydroxide. The nickel hydrogen battery is usually incorporated ina vehicle as an assembled battery in which a plurality of cells areconnected in series to increase the output voltage. In the vehicleincorporating such a nickel hydrogen battery is generally equipped witha battery monitoring apparatus for monitoring a state of the battery(e.g. refer to JP-A-2002-315212). In the nickel hydrogen battery, thecells are generally grouped into blocks. The battery monitoringapparatus detects a voltage of each of the blocks to monitor the voltageof the assembled battery.

A battery monitoring apparatus for a nickel hydrogen battery is known inwhich a circuit board, on which electronic components are mounted, isaccommodated in a housing. The circuit board is provided with ahigh-voltage part having a voltage detection circuit for detecting avoltage of an assembled battery, and a low-voltage part having alow-voltage circuit that operates at voltage lower than that of thehigh-voltage part. The low-voltage part has a function, for example, ofoutputting a signal corresponding to the detection voltage of thevoltage detection circuit to an upper ECU (e.g. hybrid ECU).

When an abnormity is caused in the assembled battery or the voltagedetection circuit, the low-voltage part outputs information on theabnormity of the high-voltage part to the upper ECU. Thereby, theabnormity can be detected by the upper ECU. In this case, when anabnormity such as a fault of the voltage detection circuit due to ashort circuit is caused, the temperature of the high-voltage part may behigher than usual. If such an abnormity is caused, it is required thatthe low-voltage part is protected from the high-voltage part whosetemperature has become higher. Specifically, the state of the nickelhydrogen battery is often monitored in block voltage. Hence, in thebattery monitoring apparatus, the temperature of the high-voltage parteasily becomes higher.

SUMMARY

An embodiment provides a battery monitoring apparatus that can prevent amalfunction of a low voltage part due to heat.

As an aspect of the embodiment, a battery monitoring apparatus isprovided which monitors a state of a nickel hydrogen battery. Theapparatus includes: a board having a high voltage part having a voltagedetection section detecting a voltage of the nickel hydrogen battery,and a low voltage part operating at voltage lower than voltage of thehigh voltage part; a housing that accommodates the board; and anattachment member that is attached to an opposed portion of the housing,which is opposed to a board surface of the board to attach the housingto a predetermined position. A passage is formed between the opposedportion and the attachment member, the passage extending from an openingpart provided at a circumference part of the housing and along theopposed portion, and the passage being located at a position thatoverlaps with the low voltage part, when viewed in a normal direction ofthe board surface.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a perspective view showing a general schematic configurationof a battery monitoring apparatus;

FIG. 2 is an exploded perspective view showing an exploded housing;

FIG. 3 is a plan view of a board;

FIG. 4 is a bottom view of the battery monitoring apparatus;

FIG. 5 is a top view of the battery monitoring apparatus;

FIG. 6 is a sectional view of a bracket;

FIG. 7 is a diagram showing a position of the bracket viewed in thenormal direction of a board surface; and

FIG. 8 is a diagram showing a position of a bracket of anotherembodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the accompanying drawings, hereinafter are describedsome embodiments of the present invention.

In the present embodiment, a battery monitoring apparatus is embodiedwhich monitors a state of an in-vehicle high-voltage battery serving asa power source of a vehicle. In the present embodiment, the in-vehiclehigh-voltage battery is a nickel hydrogen battery, and is configured asan assembled battery including a series connection of a plurality ofcells

A schematic configuration of the battery monitoring apparatus of thepresent embodiment is described with reference to FIG. 1 and FIG. 2.FIG. 1 is a perspective view showing a general schematic configurationof the battery monitoring apparatus. FIG. 2 is an exploded perspectiveview showing a partial configuration of the battery monitoringapparatus. As shown in FIG. 1 and FIG. 2, the battery monitoringapparatus 10 includes a board 11, a housing 12 accommodating the board11, and a bracket 13 serving as an attachment member. Note that, in thefollowing explanation, the vertical direction of the battery monitoringapparatus 10 is defined with reference to FIG. 1 showing a state wherethe battery monitoring apparatus 10 is placed on a horizon plane, forthe sake of convenience.

The housing 12 is a vertically separable case including a base 14 and acover 15, and is made of a metallic material such as aluminum. The base14 includes a substantially quadrangular bottom plate part 16, and astanding wall 17 standing from the bottom plate part 16. The top surfaceof the bottom plate part 16 is a board mounting part on which the board11 is mounted. In a state where the board 11 is mounted, the board 11 issurrounded by the standing wall 17.

The cover 15 includes a top board 18 that covers the board 11 fromabove, and a hanging wall 19 extending downward from the top board 18.The top board 18 has a substantially quadrangle shape. The hanging wall19 surrounds the circumference part of the top board 18. On two of sidesurfaces provided on four sides of the top board 18, an end portion 19a, which is one part of the hanging wall 19, contacts a base 14, and anend portion 19 b, which is the other part of the hanging wall 19, isapart from the base 14. From the gap between the end portion 19 b of thehanging wall 19 and the base 14, a high-voltage side connector 21 and alow-voltage side connector 22 are exposed outside. The high-voltage sideconnector 21 is electrically connected to an in-vehicle high-voltagebattery. The low-voltage side connector 22 is electrically connected toan in-vehicle upper ECU (e.g. hybrid ECU), which receives outputs of thebattery monitoring apparatus 10.

Circumference parts of the base 14 and the cover 15 are each providedwith a plurality of screw holes. The cover 15 is mounted on the base 14and is fixed to the base 14 by fixing screws N. Note that the base 14and the cover 15 may be made of synthetic resin such as polypropylene.

The board 11 is a rectangular printed circuit board, and has a boardsurface 11 a on which a predetermined circuit pattern is formed. Inaddition, various components such as the high-voltage side connector 21,the low-voltage side connector 22, and electronic components are mountedon the board surface 11 a.

The board 11 is described with reference to FIG. 3. As shown in FIG. 3,the board 11 has a high voltage part 24 and a low voltage part 23. Thehigh voltage part 24 is connected to an assembled battery 50 serving asan in-vehicle high-voltage battery. The low voltage part 23 operates atvoltage lower than that at which the high voltage part 24 operates. Thelow voltage part 23 is an area where the housing 12 is a reference ofthe potential. The high voltage part 24 is an area where the referencepotential is higher than that of the low voltage part 23. In the presentembodiment, the reference potential of the high voltage part 24 is setto a median between the potential at the positive terminal of theassembled battery 50 and the potential at the negative terminal of theassembled battery 50. The high voltage part 24 and the low voltage part23 are arranged in an area where the high voltage part 24 and the lowvoltage part 23 are not overlapped with each other when viewed in thenormal direction of the board surface 11 a, and on the same surface ofthe board.

In the high voltage part 24, a voltage detection section 25 is providedwhich detects a voltage of the assembled battery 50. The voltagedetection section 25 is configured by, for example, an operationalamplifier. In the high voltage part 24, the high-voltage side connector21 is placed at a position corresponding to the circumference part ofthe board 11. The voltage detection section 25 is electrically connectedto the assembled battery 50 via the high-voltage side connector 21. Thevoltage detection section 25 detects a voltage across the terminals ofthe cells and outputs a signal corresponding to the detected voltageacross the terminals to the low voltage part 23. Specifically, theassembled battery 50 of the present embodiment is configured by aplurality of battery blocks, each of which is a group having apredetermined number of cells, each of which is a minimum unit fordischarge and charge. The voltage detection section 25 detects a voltage(block voltage) of each of the battery blocks by using, for example, aflying capacitor system to determine whether or not the cells are in astate of overcharge or over discharge. Note that the voltage detectionsection 25 may be an integrated circuit.

In the low voltage part 23, a control section 26 is provided. Thecontrol section 26 is configured as an integrated circuit. The controlsection 26 is electrically connected to the voltage detection section 25of the high voltage part 24 via an insulating part 27 such as aphotocoupler. Note that the insulating part 27 is an insulating memberfor electrically insulating the high voltage part 24 and the low voltagepart 23 from each other. At a position of the low voltage part 23 whichis part of the circumference part of the board 11, a low-voltage sideconnector 22 is placed. The control section 26 is electrically connectedto the upper ECU via the low-voltage side connector 22. The controlsection 26 receives a signal (voltage detection signal) corresponding tothe detection voltage of the voltage detection section 25, and outputsthe received voltage detection signal to the upper ECU via thelow-voltage side connector 22. Note that, although not shown, variouselectronic components are mounted on the board 11 in addition to thevoltage detection section 25, the insulating part 27, and the controlsection 26.

The high voltage part 24 and the low voltage part 23 are arranged in thedirection along a side 11 b (hereinafter, referred to as low-voltageside connector placement side 11 b), on which the low-voltage sideconnector 22 is placed, and which is one of the four sides surroundingthe board surface 11 a. Also, the high-voltage side connector 21 isplaced on a side 11 c opposed to the low-voltage side connectorplacement side 11 b.

Next, the bracket 13 is described in detail with reference to FIG. 4 toFIG. 7. FIG. 4 is a bottom view of the battery monitoring apparatus 10.FIG. 5 is a top view of the battery monitoring apparatus 10. FIG. 6 is asectional view cut along the line VI-VI of FIG. 4. FIG. 7 is a diagramshowing a position of the bracket 13 viewed in the normal direction ofthe board surface 11 a.

The bracket 13 is an attachment member for attaching the housing 12 to apredetermined position of a vehicle, and is made of metallic materialsuch as aluminium. The bracket 13 has an elongated shape. Each of theboth end portions of the bracket 13, which are positioned in thelongitudinal direction of the bracket 13, are provided with a hole part31. Inserting fixing screws into the hole parts 31 fixes the housing 12to a predetermined position of the vehicle side. Note that the bracket13 may be formed of synthetic resin such as polypropylene.

The bracket 13 is attached to an outer surface 16 a of the bottom platepart 16, which is an opposed portion opposed to the board surface 11 a,of the housing 12 by welding, screw fastening, adhesion or the like. Thebracket 13 has a length in the longitudinal direction longer than thelength of the side of the bottom plate part 16 extending in thedirection same as the direction in which the bracket 13 extends.Specifically, as shown in FIG. 4, the bracket 13 has an overlapped part13 a and protrusion parts 13 b. The overlapped part 13 a is opposed toand overlaps with the housing 12 in a state where the overlapped part 13a is attached to the bottom plate part 16. The protrusion parts 13 bprotrude from the housing 12. Each of the protrusion parts 13 b isprovided with a hole part 31. The battery monitoring apparatus 10 isattached to a predetermined position of the vehicle with reference tothe hole parts 31.

More specifically, as shown in FIG. 6, the bracket 13 has fixing parts13 c and a convex part 13 d. The fixing parts 13 c are provide in theoverlapped part 13 a and are fixed to the outer surface 16 a of thebottom plate part 16 of the housing 12. The convex part 13 d laterallyprotrudes from the outer surface 16 a of the bottom plate part 16. Thefixing parts 13 c are provided at both sides of the convex part 13 d inthe direction perpendicular to the longitudinal direction of the bracket13 so as to put the convex part 13 d between the fixing parts 13 c. Thebracket 13 is attached to the housing 12 by fixing the fixing parts 13 cto the outer surface 16 a of the bottom plate part 16. In addition, asshown in FIG. 6, in the above attachment state, a clearance space isformed (provided) between the bottom plate part 16 and the convex part13 d.

The clearance space extends from one end portion to the other endportion of the convex part 13 and in the longitudinal direction of theconvex part 13. Opening parts 33 are formed at circumference parts 12 aof the housing 12 as ports of the clearance space between the bottomplate part 16 and the convex part 13 d. A passage 34 is formed by theclearance space extending from the opening part 33 and along the bottomplate part 16 to function as a ventilation passage. In addition, theopening parts 33 are formed at boundaries between the overlapped part 13a and the protrusion parts 13 b.

The convex part 13 d has a flat part 13 e extending parallel to thebottom plate part 16. In a state where the battery monitoring apparatus10 is fixed to a predetermined position of the vehicle, at least part ofthe flat part 13 e is brought into contact with the vehicle side. Inaddition, the passage 34 has a flattened shape having a predeterminedheight (e.g. several millimeters) due to the convex part 13 d. Note thatthe cross-sectional shape of the bracket 13 is not limited to theflattened shape shown in FIG. 6, but may be, for example, a circularshape or a V shape.

In a state where the battery monitoring apparatus 10 is attached to thevehicle side via the bracket 13, the housing 12 is apart from anattachment part of the vehicle side. That is, a gap is provided betweenthe vehicle side and the housing 12. In the present embodiment, sincethe passage 34 is formed in the longitudinal direction of the bracket 13and between the housing 12 and the bracket 13, the direction in whichair flows can be restricted. Hence, the ventilation can be provided in adesired direction. In addition, in a state where the battery monitoringapparatus 10 is attached to the vehicle, the convex part 13 d (flat part13 e) of the bracket 13 serves as an attachment surface to the vehicle.Since the convex part 13 d is wide, the battery monitoring apparatus 10is stably attached.

In addition, the width of the convex part 13 d varies when viewed in thelongitudinal direction of the bracket 13. Specifically, in the bracket13, the widths of the opening parts 33 positioned at the circumferenceparts 12 a of the housing 12 differ from the width of the centralportion, and the widths of the opening parts 33 are larger than thewidth of the central portion. Hence, air easily flows into the openingpart 33, which is an inlet port of ventilation to the passage 34. Inaddition, according to the configuration, the air flow velocity in thevicinity of the center of the bottom plate part 16 can be higher. Next,the arrangement of the bracket 13 is described. As shown in FIG. 7, thebracket 13 is positioned at a position where the passage 34 formedbetween the bracket 13 and the housing 12 overlaps with the low voltagepart 23 viewed in the normal direction of the board surface 11 a.

Specifically, as shown in FIG. 7, the bracket 13 is placed so as tocross the low-voltage side connector placement side 11 b and the side 11c opposed to the low-voltage side connector placement side 11 b, whenviewed in the normal direction of the board surface 11 a. The bracket 13is attached so that the passage 34 overlaps with only the low voltagepart 23 when viewed in the normal direction of the board surface 11 a.In the present embodiment, the bracket 13 is attached so that thepassage 34 overlaps with the control section 26.

A system, which detects block voltages to monitor the voltage of theassembled battery 50, is required to monitor high voltage compared witha system that detects a voltage of each cell to monitor the voltage ofthe assembled battery 50. Hence, the high voltage part 24 easily becomeshigh in temperature. When the high voltage part 24 is excessively highin temperature, there is a concern that the low voltage part 23 maydecrease in function due to the influence of heat. Specifically, thecontrol section 26 may not be able to output various pieces ofinformation to the upper ECU. In this regard, according to the batterymonitoring apparatus 10 of the present embodiment, since the passage 34formed in the longitudinal direction of the bracket 13 serves as aventilation path, a flow of air can be produced below the low voltagepart 23. Hence, even when the high voltage part 24 becomes excessivelyhigh in temperature, the flow of air in the passage 34 can promote theheat radiation from the low voltage part 23, which communicates with theupper ECU. According to the present embodiment described above, thefollowing advantages can be provided.

The passage 34 is formed which extends between the bracket 13 and thebottom plate part 16 of the housing 12 and along the bottom plate part16 from the opening part 33 provided at the circumference part of thehousing 12 to the bottom plate part 16 of the housing 12. In addition,the bracket 13 is placed so that the passage 34 overlaps with the lowvoltage part 23 when viewed in the normal direction of the board surface11 a. According to the configuration, the passage 34 serves as aventilation path. Hence, when the high voltage part 24 is excessivelyhigh in temperature, the flow of air in the passage 34 canpreferentially and intensively draw heat from the low voltage part 23,which communicates with the upper ECU. In addition, such promotion ofthe heat radiation can prevent a malfunction of the low voltage part 23.As a result, even when the high voltage part 24 is abnormal, powerperformance and evacuation travel performance of the vehicle can beprevented from lowering. Hence, the user can safely stop the vehicle.

In addition, the high voltage part 24 and the low voltage part 23 areconnected via the insulating part 27. When the high voltage part 24 isexcessively high in temperature, controlling the operation of theinsulating part 27 can separate the high voltage part 24 from the lowvoltage part 23. Such separation of the high voltage part 24 and thepromotion of the heat radiation from the low voltage part 23 using thepassage 34 formed between the bracket 13 and the housing 12 can protectthe low voltage part 23 from heat. In addition, information can becommunicated to the upper CPU.

The bracket 13 has the overlapped part 13 a, which is opposed to andoverlaps with the housing 12 in a state where the bracket 13 is attachedto the bottom plate part 16, and the protrusion parts 13 b protrudingfrom the housing 12. In the bracket 13, the opening parts 33 are formedat boundaries between the overlapped part 13 a and the protrusion parts13 b. The air flowing around the battery monitoring apparatus 10 flowsalong the protrusion part 13 b of the bracket 13, and flows into thepassage 34 through the opening part 33 positioned at the boundarybetween the protrusion part 13 b and the overlapped part 13 a. Hence, aconfiguration can be realized which easily introduces air into thepassage 34.

The high voltage part 24 and the low voltage part 23 are arranged in thedirection along the low-voltage side connector placement side 11 b,which is one of the four sides forming the board surface 11 a. Thebracket 13 is placed so as to cross the low-voltage side connectorplacement side 11 b and the side 11 c opposed to the low-voltage sideconnector placement side 11 b. When the low-voltage side connector 22 isprovided on a side surface of the housing 12, the flow of air passingthrough the gap between the low-voltage side connector 22 and thehousing 12 is easily generated. In this case, the above configurationeasily introduces air into the passage 34.

In the present embodiment, the high-voltage side connector 21 isprovided on the side 11 c opposed to the low-voltage side connectorplacement side 11 b. The bracket 13 is placed so as to cross thelow-voltage side connector placement side 11 b and the high-voltage sideconnector placement side 11 c. When two connectors are arranged on theside surfaces of the housing 12 so as to be opposed to each other, theflow of air passing from the gap between one of the connectors and thehousing 12 to the gap between the other of the connectors and thehousing 12 is easily generated. In this case, the above configurationeasily introduces air into the passage 34.

The bracket 13 has the fixing parts 13 c, which is fixed to the outersurface 16 a of the bottom plate part 16 of the housing 12 in theoverlapped part 13 a, and the convex part 13 d, which laterallyprotrudes from the outer surface 16 a of the bottom plate part 16.According to the configuration, the passage 34 can be formed between thebracket 13 and the outer surface of the bottom plate part 16 withoutcomplicating the structure of the housing 12.

The flat part 13 e of the bracket 13 can stably attach the batterymonitoring apparatus 10 to the vehicle side by the flat part 13 e. Inaddition, since the cross-sectional shape of the passage 34 is aflattened shape, the cross-sectional area of the passage for ventilationcan be ensured without excessively making larger the distance (deadspace) from the vehicle side to the housing 12.

The bracket 13 is expected to function as a heat radiation partradiating heat by heat transfer. That is, placing the bracket 13 at theposition where the bracket 13 overlaps with the low voltage part 23 in aplanar view can radiate the heat in the low voltage part 23 to thevehicle side (vehicle body) via the bracket 13.

Other Embodiments

It will be appreciated that the present invention is not limited to theconfigurations described above, but any and all modifications,variations or equivalents, which may occur to those who are skilled inthe art, should be considered to fall within the scope of the presentinvention.

In the above embodiment, as shown in FIG. 7, the high-voltage sideconnector 21 is placed on the side 11 c opposed to the low-voltage sideconnector placement side 11 b. The position where the high-voltage sideconnector 21 is attached is not particularly limited with respect to theposition where the low-voltage side connector 22 is attached. Forexample, the high-voltage side connector 21 may be attached on the sideperpendicular to the low-voltage side connector placement side 11 b onthe circumference part of the high voltage part 24. Alternatively, thehigh-voltage side connector 21 may be attached on the same side as thelow-voltage side connector placement side 11 b.

In the above embodiment, the high-voltage side connector 21 is placed onthe side 11 c opposed to the low-voltage side connector placement side11 b. The bracket 13 is placed so as to cross the low-voltage sideconnector placement side 11 b and the high-voltage side connectorplacement side 11 c when viewed in the normal direction of the boardsurface 11 a. However, the bracket 13 may be placed so as to cross thelow-voltage side connector placement side 11 b and the side on which thehigh-voltage side connector 21 and the low-voltage side connector 22 arenot placed.

The placement of the bracket 13 to the board surface 11 a is not limitedto the above embodiment. For example, as shown in FIG. 8, in a statewhere the high voltage part 24 and the low voltage part 23 are arrangedin the direction crossing the low-voltage side connector placement side11 b of the four sides surrounding the board surface 11 a, the bracket13 is placed so as to cross the opposed two sides 11 d and 11 e on whichthe low-voltage side connector 22 and the high-voltage side connector 21are not provided. Note that, in FIG. 8, the high-voltage side connector21 is placed on the side 11 c opposed to the low-voltage side connectorplacement side 11 b. When two connectors are placed so as to be opposedto each other on the side surfaces of the housing 12, the flow of airpassing from the gap between one of the connectors and the housing 12 tothe gap between the other of the connectors and the housing 12 is easilygenerated. In such a configuration, placing the bracket 13 so as tocross the two sides 11 d and 11 e can promote the flow of air in thedirection crossing the direction in which the low-voltage side connector22 and the high-voltage side connector 21 are arranged.

In the above embodiment, providing the convex part 13 d to the bracket13 provides the passage 34 in a clearance space between the bracket 13and bottom plate part 16 of the housing 12. However, a concave part maybe provided in the bottom plate part 16 and at the position thatoverlaps with the low voltage part 23 when viewed in the normaldirection of the board surface 11 a, and the bracket 13 may be attachedat the position that overlaps with the concave part, to provide thepassage 34 between the bracket 13 and the housing 12. In this case, asin the case of the above embodiment, the bracket 13 may have the fixingparts 13 c and the convex part 13 d, or may have a flat plate shape.

In the above embodiment, the bracket 13 serving as an attachment memberis configured by one component. However, the bracket 13 may beconfigured by two or more components. For example, when two brackets 13are attached to the battery monitoring apparatus 10, the two brackets13, which are provided by cutting off an intermediate part in thelongitudinal direction of the bracket 13 shown in FIG. 4, may beattached to the housing 12.

In the above embodiment, the bracket 13 is attached to the bottom platepart 16 of the base 14 of the housing 12. However, the bracket 13 may beattached to the top board 18 of the cover 15.

The passage 34 in a planar view of the bottom plate part 16 of thehousing 12 may have a straight shape extending along the bottom platepart 16 or a curved shape. The bracket 13 may have a branched shape.According to this, the passage 34 may have a branched shape.

In the above embodiment, one board 11 having the high voltage part 24and the low voltage part 23 is accommodated in the housing 12. However,two or more boards 11 may be accommodated in the housing 12, one of theboards 11 having the high voltage part 24, and another of the boards 11having the low voltage part 23. Note that the board having the highvoltage part 24 and the board having the low voltage part 23 arearranged so that at least part of the high voltage part 24 and at leastpart of the low voltage part 23 are not overlapped with each other, whenviewed in the normal direction of the board surface 11 a. The bracket 13is attached so as to overlap with only the low voltage part 23 in aplanar view of the board surface 11 a.

In the above embodiment, although the battery monitoring apparatus 10 isapplied to a nickel hydrogen battery incorporated in a vehicle, thebattery monitoring apparatus 10 may be applied to a nickel hydrogenbattery used for an object other than the vehicle (e.g. electricalequipment).

Hereinafter, aspects of the above-described embodiments will besummarized.

As an aspect of the embodiment, a battery monitoring apparatus (10) isprovided which monitors a state of a nickel hydrogen battery (50). Theapparatus includes: a board (11) having a high voltage part (24) havinga voltage detection section (25) detecting a voltage of the nickelhydrogen battery, and a low voltage part (23) operating at voltage lowerthan voltage of the high voltage part; a housing (12) that accommodatesthe board; and an attachment member (13) that is attached to an opposedportion (16) the housing, which is opposed to a board surface (11 a) ofthe board to attach the housing to a predetermined position. A passage(34) is formed between the opposed portion and the attachment member,the passage extending from an opening part (33) provided at acircumference part of the housing and along the opposed portion, and thepassage being located at a position that overlaps with the low voltagepart, when viewed in a normal direction of the board surface.

In the battery monitoring apparatus, the passage is formed which extendsbetween the attachment member and the housing and along the opposedportion of the housing side from the opening part provided at thecircumference part of the housing. In addition, the attachment member isplaced so that the passage overlaps with the low voltage part, whenviewed in the normal direction of the board surface. According to theconfiguration, the passage provided between the attachment member andthe housing serves as a ventilation path. Hence, when the high voltagepart is excessively high in temperature, the flow of air in the passagecan preferentially and intensively draw heat from the low voltage part.In addition, such promotion of the heat radiation can prevent amalfunction of the low voltage part.

What is claimed is:
 1. A battery monitoring apparatus that monitors astate of a nickel hydrogen battery, the apparatus comprising: a boardhaving a high voltage part having a voltage detection section detectinga voltage of the nickel hydrogen battery, and a low voltage partoperating at voltage lower than voltage of the high voltage part; ahousing that accommodates the board; and an attachment member that isattached to an opposed portion of the housing, which is opposed to aboard surface of the board to attach the housing to a predeterminedposition, wherein a passage is formed between the opposed portion andthe attachment member, the passage extending from an opening partprovided at a circumference part of the housing and along the opposedportion, and the passage being located at a position that overlaps withthe low voltage part, when viewed in a normal direction of the boardsurface.
 2. The battery monitoring apparatus according to claim 1,wherein the fixing member has an overlapped part that is opposed to andoverlaps with the housing in a state where the attachment member isattached to the opposed portion, and a protrusion part that protrudesfrom the housing, and the opening part is formed at a boundary betweenthe overlapped part and the protrusion part.
 3. The battery monitoringapparatus according to claim 1, wherein the board has a rectangularshape, a low-voltage side connector is placed on the board and at aposition corresponding to a circumference part of the board in the lowvoltage part, the low-voltage side connector electrically connecting thelow voltage part and a unit that receives an output of the batterymonitoring apparatus, the high voltage part and the low voltage part arearranged in a direction along a connector placement side, on which thelow-voltage side connector is provided, of the board surface, and theattachment member is placed so as to cross the connector placement sideand a side opposed to the connector placement side, when viewed in anormal direction of the board surface.
 4. The battery monitoringapparatus according to claim 3, wherein a high-voltage side connector isplaced on the board and at a position corresponding to a circumferencepart of the board in the high voltage part, the high-voltage sideconnector electrically connecting the nickel hydrogen battery and thehigh voltage part, and the high-voltage side connector is provided on aside opposed to the connector placement side of the board surface. 5.The battery monitoring apparatus according to claim 1, wherein the boardhas a rectangular shape, a low-voltage side connector is placed on theboard and at a position corresponding to a circumference part of theboard in the low voltage part, the low-voltage side connectorelectrically connecting the low voltage part and a unit that receives anoutput of the battery monitoring apparatus, and a high-voltage sideconnector is placed on the board and at a position corresponding to acircumference part of the board in the high voltage part, thehigh-voltage side connector electrically connecting the nickel hydrogenbattery and the high voltage part, the high voltage part and the lowvoltage part are arranged on the board surface and in a directioncrossing a connector placement side, on which the low-voltage sideconnector is placed, the high-voltage side connector is provided on theboard surface and on a side opposed to the connector placement side, andthe attachment member is placed so as to cross two sides different fromthe connector placement side and the side opposed to the connectorplacement side, when viewed in a normal direction of the board surface.6. The battery monitoring apparatus according to claim 1, wherein theattachment member has a fixing part, which is fixed to the opposedportion in an overlapped part that is opposed to and overlaps with thehousing in a state where the attachment member is attached to theopposed portion, and a convex part that laterally protrudes from theopposed portion.